Automatic spray applicators have wide ranging use for the application of coatings of various types on objects during manufacture. For example, parts for automobile vehicle bodies commonly are coated using robotic devices with spray applicators. The robot is programmed to perform a sequence of maneuvers so that the vehicle body pieces are adequately and precisely covered in a rapid procedure with minimal waste of coating.
Atomizing applicators have been used to reduce the amount of overspray and further reduce waste. In a known atomizing applicator, a bell cup rotates at high speed, and the coating material, such as paint, is provided to the inside of the bell cup. As the paint or other coating moves outwardly and off the bell cup surface as a result of centrifugal force, the coating is atomized into a fine mist and directed at the object to be coated. It is known to direct air streams along the outside of the cup to confine and direct the atomized coating toward the object being coated. It is also known to electrically charge the atomized mist with electrical potential and to ground the object being coated so that the coating material is attracted to the object, further reducing overspray and improving coverage on irregularly shaped target objects.
In present day manufacturing procedures, such as for automobile vehicle bodies, it is common to have parts in random color sequence advancing along the manufacturing line. Thus, for each object to be coated it may be necessary to change the color of paint or the type of coating used from that used for the previous object. Thirty or more different colors may be available to consumers purchasing automobiles, and at any point in the manufacturing process any of the colors may be necessary for coating the object that is placed before the robot. The time required for changing from one coating to another coating should be kept short, so that the painting robot performance does not become a significant limiting factor in the manufacturing speed on the assembly line. In an advantageous system, the time required for changing the coating is no longer than the time necessary to move a completed object from in front of the robot and to move the next target object into position for coating.
With the growing popularity of water based coatings, partly due to environmental concerns and regulations, problems are presented not only in providing rapid changes in coating type, but also in isolating portions of the applicator system that are at high electrical potential from other portions of the system at low electrical potential, in that the coatings are conductive.
It has been proposed to use interchangeable canisters with an applicator that is separated from a station at which the canisters are filled. Various constructions have been proposed for replacing emptied canisters with filled canisters. These systems require not only the aforementioned cleaning of common parts of the applicator system, but also rapid physical exchange of canisters during the change cycle when one object already coated is replaced by the next object to be coated.